convert a list of objects from one type to another using lambda expression
C#GenericsLambdaC# Problem Overview
I have a foreach loop reading a list of objects of one type and producing a list of objects of a different type. I was told that a lambda expression can achieve the same result.
var origList = List<OrigType>(); // assume populated
var targetList = List<TargetType>();
foreach(OrigType a in origList) {
targetList.Add(new TargetType() {SomeValue = a.SomeValue});
}
Any help would be appreciated- i'm new to lambda and linq thanks, s
C# Solutions
Solution 1 - C#
Try the following
var targetList = origList
.Select(x => new TargetType() { SomeValue = x.SomeValue })
.ToList();
This is using a combination of Lambdas and LINQ to achieve the solution. The Select function is a projection style method which will apply the passed in delegate (or lambda in this case) to every value in the original collection. The result will be returned in a new IEnumerable<TargetType>
. The .ToList call is an extension method which will convert this IEnumerable<TargetType>
into a List<TargetType>
.
Solution 2 - C#
If you know you want to convert from List<T1>
to List<T2>
then List<T>.ConvertAll
will be slightly more efficient than Select
/ToList
because it knows the exact size to start with:
target = orig.ConvertAll(x => new TargetType { SomeValue = x.SomeValue });
In the more general case when you only know about the source as an IEnumerable<T>
, using Select
/ToList
is the way to go. You could also argue that in a world with LINQ, it's more idiomatic to start with... but it's worth at least being aware of the ConvertAll
option.
Solution 3 - C#
var target = origList.ConvertAll(x => (TargetType)x);
Solution 4 - C#
List<target> targetList = new List<target>(originalList.Cast<target>());
Solution 5 - C#
I believe something like this should work:
origList.Select(a => new TargetType() { SomeValue = a.SomeValue});
Solution 6 - C#
Here's a simple example..
List<char> c = new List<char>() { 'A', 'B', 'C' };
List<string> s = c.Select(x => x.ToString()).ToList();
Solution 7 - C#
var list1 = new List<Type1>();
var list2 = new List<Type2>();
list1.ForEach(item => list2.Add(new Type2() { Prop1 = value1 }));
Solution 8 - C#
Assume that you have multiple properties you want to convert.
public class OrigType{
public string Prop1A {get;set;}
public string Prop1B {get;set;}
}
public class TargetType{
public string Prop2A {get;set;}
public string Prop2B {get;set;}
}
var list1 = new List<OrigType>();
var list2 = new List<TargetType>();
list1.ConvertAll(x => new OrigType { Prop2A = x.Prop1A, Prop2B = x.Prop1B })
Solution 9 - C#
Or with a constructor
& linq
with Select
:
public class TargetType {
public string Prop1 {get;set;}
public string Prop1 {get;set;}
// Constructor
public TargetType(OrigType origType) {
Prop1 = origType.Prop1;
Prop2 = origType.Prop2;
}
}
var origList = new List<OrigType>();
var targetList = origList.Select(s=> new TargetType(s)).ToList();
The Linq
line is more soft! ;-)
Solution 10 - C#
If you need to use a function to cast:
var list1 = new List<Type1>();
var list2 = new List<Type2>();
list2 = list1.ConvertAll(x => myConvertFuntion(x));
Where my custom function is:
private Type2 myConvertFunction(Type1 obj){
//do something to cast Type1 into Type2
return new Type2();
}
Solution 11 - C#
for similar type class.
List<targetlist> targetlst= JsonConvert.DeserializeObject<List<targetlist>>(JsonConvert.SerializeObject(<List<baselist>));
Solution 12 - C#
If the types can be directly cast this is the cleanest way to do it:
var target = yourList.ConvertAll(x => (TargetType)x);
If the types can't be directly cast then you can map the properties from the orginal type to the target type.
var target = yourList.ConvertAll(x => new TargetType { SomeValue = x.SomeValue });
Solution 13 - C#
We will consider first List type is String and want to convert it to Integer type of List.
List<String> origList = new ArrayList<>(); // assume populated
Add values in the original List.
origList.add("1");
origList.add("2");
origList.add("3");
origList.add("4");
origList.add("8");
Create target List of Integer Type
List<Integer> targetLambdaList = new ArrayList<Integer>();
targetLambdaList=origList.stream().map(Integer::valueOf).collect(Collectors.toList());
Print List values using forEach:
targetLambdaList.forEach(System.out::println);